Processes for converting zero-valent metals photographic images to formazan dye images

ABSTRACT

A zero valent metal image in which the metal has a standard oxidation potential more positive than -0.98 volt is advantageously converted to a nondiffusible formazan dye image by the single process step of contacting the metal image with a solution of a tetrazolium salt that contains a metal complexing moiety when the combination of tetrazolium salt, metal and water produces a solution reaction potential E of at least +0.01 volt.

United States Patent Brault et a].

PROCESSES FOR CONVERTING ZERO- VALENT METALS PHOTOGRAPHIC IMAGES TO FORMAZAN DYE IMAGES Albert T. Brault, Rochester; Vernon L. Bissonette, Brockport, both of NY.

Eastman Kodak Company, Rochester, NY.

Feb. 25, 1970 Inventors:

Assignee:

Filed:

Appl. No.:

15] 3,655,382 Apr. 11,1972

[56] References Cited FORElGN PATENTS OR APPLlCATlONS 670,883 4/1952 Great Britain ..96/54 Primary ExaminerNorman G. Torchin Assistant ExaminerAlfons0 T. Suro Pico Attorney-W. H. J. Kline, J. R. Frederick and R. C. Livermore [57] ABSTRACT A zero valent metal image in which the metal has a standard oxidation potential more positive than -0.98 volt is advantageously converted to a nondiffusible formazan dye image by the single process step of contacting the metal image with a solution of a tetrazolium salt that contains a metal complexing moiety when the combination of tetrazolium salt, metal and water produces a solution reaction potential E of at least +0.01 volt.

11 Claims, No Drawings This invention is related to photography, compositions for use in photographic processing, photographic processes for forming high density dye images from photographic metal images and processes for the removal of metal images from a developed photographic element.

In photography, it is sometimes desired to convert a photographic metal image into a dye image or to add to a photographic silver image a corresponding dye image. Processes are desired that will make it possible to obtain photographic reproductions having good image densities with elements containing less silver than usual or with photographic silver images having lower image densities than needed. In X-ray photography, for example, it is desirable to be able to reduce the exposure of a patient being X-rayed as much as possible and still obtain a useful picture.

British Pat. No. 908,299 describes a process for converting a silver image in a photographic emulsion layer into a formazan dye image by treating the silver image with a tetrazolium salt in the presence of cyanide ions, and subsequently bleaching with a ferricyanide bromide bleach bath, followed by washing, fixing with a sodium thiosulphate bath, washing and drying. The use of cyanide ion is very undesirable because of the danger to the operating personnel. Furthermore, the process described by the British patent requires a separate, additional bleach, fix and three intermediate washing steps in order to remove the silver image left after forming the formazan dye image.

It is therefore an object of our invention to provide a novel, single-step process for converting a photographic metal image into a dye image.

Another object of our invention is to provide a novel, singlestep process for converting a metal image to a formazan dye image and, simultaneously, to remove the metal image from a black-and-white developed photographic element.

Still another object of our invention is to provide a novel process which is valuable for the conversion of even a low density silver image into a high density formazan dye image or, alternatively, into the high density formazan dye image plus the silver image.

Still other objects of our invention will become apparent from a consideration of the following specification and claims.

These and still other objects of our invention are accomplished by our novel process comprising the step of contacting a metal image having a standard oxidation potential more positive than O.98 volts with an aqueous solution of a diffusible tetrazolium salt (T-salt) which has at least one moiety that is a metal ion complexing agent, until the T-salt oxidizes the metal image to the corresponding metal ion complex and, simultaneously converts the metal image to a corresponding formazan dye image. Our solution of the T-salt requires no source of metal complexing agent in addition to the metal complexing agent that is an integral part of the T-salt molecule. Our process does not require a separate bleach step followed by a wash step, a fix step and another washing step as is required by the prior art.

The combination of the zero valent metal image with our T- salt in the presence of water produces a solution reaction potential E of at least +0.01 volt. The solution reaction potential E is defined by the following formula:

in which a and b are each integers of from I to 3 determined by the stable oxidation state of metal ion and which are needed to satisfy the stochiometric relationship of the reaction of metal with T-salt; d represents the number of electrons transferred in said reaction: E".\m .u"" and E"rm-m- 'I'-xulr are the standard oxidation potentials for (1) zero valent metal to metal ion of valence m and (2) formazan dye to T-salt, respectively, [M [Formazan], ]T-salt]and [H ]represent the concentrations of the indicated material. Standard oxidation potentials are for unit activity at 25 C as referred to the hydrogen-hydrogen ion couple as zero volts. [See Handbook of Chemistry and Physics, 41st edition, page 1,733 1959).]

The formazan dye image remains at the site of the original zero valent metal image that has been converted to the complexed metal ion image. The complexed metal ion image is either allowed to remain, is removed by a fixing step or is converted back to the zero valent metal image by a chemical reduction step to produce a formazan dye plus metal image corresponding to the original metal image. Where it is desired to increase the formazan dye image density formed by our process, the reformed metal image is contacted with more of our T-salt solution to form more formazan dye and metal ion complex in the areas where the original metal image existed.

, The metal ion complex is either allowed to remain, is removed by a fixing step or is again converted back to the metal image by a chemical reduction step so that it can either augment the formazan dye image or be used as described before to produce still more formazan dye image. This series is repeated until the density of the formazan dye image is as high as desired. In this way, even a very low density original metal image is advantageously converted to a very high density image comprising formazan dye alone, formazan dye plus complexed metal ion or formazan dye plus reformed metal image.

The metal ion complex is advantageously reduced to the corresponding metal by any appropriate chemical reduction process. For example, a complexed silver ion is advantageously made developable by contacting with a chemical fogging agent or when the complexed silver is light-sensitive, flashing to light, and then contacting with a conventional silver halide developing agent in aqueous alkaline solution to convert the developable silver complex to silver.

Any water-soluble, diffusible T-salts that will themselves strongly complex metal ions are used to advantage according to our invention. Their complexing ability is in the cation and/or in the anion portion of the T-salt. Typical T-salt cations that have metal ion complexing moiety, have attached to at least one of the 2-, 3- or 5-positions, a group containing a 5- or 6-membered heterocyclic ring having at least one nitrogen atom as a hetero atom in the ring, e.g., a thiazole nucleus, a benzothiazole nucleus, a naphthothiazole nucleus, a benzimidazole nucleus, a naphthimidazole nucleus, a pyridine nucleus, etc. The position(s) 2, 3 or 5 that are not substituted by the heterocyclic group with metal complexing moieties are advantageously substituted by any of the usual groups that are found on water-soluble and diffusible T-salts. Typical T-salt anions that complex metals are iodide, bromide, chloride,

thiocyanate, thiosulfate, etc.

The water-soluble, diffusible tetrazolium salts used to advantage according to our invention, are represented by the following formulas:

wherein R, and R each represent a group such as an aryl group, e.g., a phenyl group (e.g., phenyl, tolyl, butylphenyl, a hydroxyphenyl group, an alkali metal or ammonium salt of carboxyphcnyl, a carboxyphenyl group, an ethoxycarbonylphenyl group, an aminophenyl group, a carbamylphenyl group, a sulfophenyl group, an alkali metal or ammonium salt of a sulfophenyl group, a sulfonamidophenyl group, a sulfamylphenyl group, a mercaptophenyl group, a nitrophenyl group, etc.) a naphthyl group (e.g., naphthyl, B-naphthyl, carboxynaphthyl group, a hydroxynaphthyl group, a sulfonaphthyl group, a mercaptonaphthyl group, an aminonaphthyl group, a carbamylnaphthyl group, a sulfonamidonaphthyl group, a sulfamylnaphthyl group, a nitronaphthyl group, etc.) etc., and a heterocyclic group, preferably containing from to 6 atoms, and preferably containing hetero atoms, such as nitrogen, sulphur, oxygen and selenium, such as, for example, a thiazolyl group, a benzothiazolyl group, a selenazolyl group, a benzoselenazolyl group, a benzimiazolyl group, a naphthimidazolyl group, a triazinyl group, a pyrimidinyl group, a pyridyl group, a quinolyl group, a thienyl group, etc; R represents any of the groups represented by R and, in addition, represents an alkyl group (e.g., methyl, butyl, hexyl, dodecyl, mercaptomethyl, mercaptoethyl, etc.) etc., hydrogen, hydroxyl, carboxyl, a salt of a carboxyl group (e.g., an alkali metal salt or ammonium salt), a carboxy ester group (e.g., methoxycarbonyl, ethoxycarbonyl, phenoxycarbonyl, etc.), an amino group (e.g., amino, ethylamino, dimethylamino, anilino, etc.), a carbamyl group (e.g., carbamyl, ethylcarbamyl, dimethylcarbamyl, phenylcarbamyl, etc. sulfo, a salt of a sulfo group (e.g., an alkali metal salt), a sulfoamido group (e.g., methylsulfonamido, butylsulfonamido, phenylsulfonamido, etc.), a sulfamyl group (e.g., sulfamyl, methylsulfamyl, butyl sulfamyl, phenylsulfamyl, etc.), the mercapto group, the nitro group, or any other substituent cited as being present in this position of the formazan or the tetrazolium salt in Chem. Rev. 55, 355-483 (i955); and the substituents R and R; can advantageously contain an electron-sharing group capable of forming metal chelates or complexes, such as primary, secondary and tertiary amino, substituted amino, oxime, thioether, keto, thioketo, hydroxyl, mercapto, carboxyl, sulfo, phospho, alkoxy groups or complexes; X represents an anion (e.g., chloride, iodide, bromide, thiocyanate, thiosulfate, sulfate, paratolulenesulfonate, methylsulfate, ethylsulfate, nitrate, acetate, perchlorate, perborate, sulfite, hydroxide, carbonate, etc.); such that at least one of R R and R represents a thiazolyl nucleus, a benzothiazolyl nucleus, a naphthothiazolyl nucleus, a benzimidazolyl nucleus, a naphthimidazolyl nucleus, or a pyridyl nucleus and/or X represents a chloride ion, a bromide ion, an iodide ion, a thiocyanate ion or a thiosulfate ion; D represents a divalent aromatic group (e.g., a phenylene, diphenylene, napththalene, phenylmethylphenyl, etc); and E represents a divalent group such as an alkylene group (e.g., methylene, ethylene, propylene, butylene, etc.), an arylene group (e.g., phenylene, napththalene, diphenylene, etc.), an arylene alkylene group, for example, a phenylene alkylene group (e.g., phenylene methylene, phenylene butylene, phenylene hexylene, etc), a naphthylene alkylene group (e.g., naphthylene methylene, naphthylene butylene, naphthylene propylene, etc. etc; n represents an integer of from 1 to 5.

Tetrazolium salts used to advantage according to our invention include the following representative compounds:

T-salt No. T-salt name 1 2-(benzolthiazole-2yl)3-phenyl-5-(ochlorophenyl)-2H tetrazolium chloride 2 2-14,5dimethylthiazol2yl)-3,5-diphenyl2H- tetrazolium bromide 3 3,5-diphenyl-2-( 4phenylthiazol--yl)-2H-tetrazolium iodide 4 5 (4,5dimethylthiazole-2-yl)-2,3-diphenyl-2H- tctrazolium chloride 5 2-(benzothiazol-Lyl)-3-phenyl-5-(thien-2yl)-2H tetrazolium chloride 6 2,3-diphcnyl-5-(pyrid-2-yl)-2l-l-tetrazolium bromide 7 2,3-diphenyl-5(pyrid-4-yl)2H-tetrazolium chloride 8 2,5diphenyl-3-(pyrid-3-yl )-2Htetrazoliurn chloride 10 2,3-diphenyl-5-(benzimidazol-Z-yl)-2H-tetrazolium chloride 1 l 2,3-di(4-brornophenyl )-5-(benzothiazol-2-yl )-2H- tetrazolium chloride 12 2-[benzothiazole-2-yl 3-phenyl-5-( 2-phenyltriazol-5 -yl)-2H-tetrazolium chloride 13 2,2'-di(benzothiazol-2-yl)-3,3'-diphenyl-5,5

diethylene di-(ZH-retrazolium chloride) 14 2,2-di(benzothiazol-2-yl )-3,3 '-diphenyl-5,5 di- 1 ,6-

hexylene di-(ZH-tetrazolium chloride) 16 5,5-di(thiazol-Lyl)3.3'-diphenyl-2,2-di-pdiphenylene di-( ZH-tetrazolium chloride) 17 3,3'-di(thiazol-Z-yl)-5,5'-di(thien-2-yl)-2,2'-dip- (3 ,3 "di-methoxy-diphenylene) di-(2H-tetrazolium chloride) 17 3,3, 5,5'-tetraphenyl-2,2'-syn-p-phenylthiourea di- (ZH-tetrazolium bromide) 19 2,2, 3,3, -tetra (pyrid-2-yl)-S,5-p-phenylene ethylene di-(ZH-telrazolium chloride) 20 2-(benzothiazol-2-yl)-5-(4-acetamidophenyl)-3-(4- phenylazophenyl)2H-tetrazolium bromide 21 2- (benzothiazol-Z-yl )-3-( 4-methoxyphenyl )-5- phenyl-2Htetrazolium bromide 22 2-(4,5-dimethylihiazol-2-yl) 3,5-diphenyl-2H- tetrazolium bromide 23 2-(4-chlorophenyl)-3-(2-chlorophenyl)-5-(pyrid2- yl)-2H-ietrazollum iodide 24 2-(benzimidazol-2-yl)-5-( Z-chlorophenyl)-3-phenyl- ZH-tetrazolium chloride 25 3,5-diphenyl-2-(pyrid-2-yl)-2H-tetrazolium chloride 26 3-(benzothiazol-Zyl)-5-phenyl-2-(triazin-2-yl)2H- tetrazolium chloride 27 2,5-di(benzothiazol-2-yl)-3-(p-hydroxyphenyl)-2H- tetrazolium chloride 28 B-(wcarboxyphenyl)-5-methyl-2-(4 phenylthiazol 2- yl)-2H-tetrazolium bromide 29 3-(o-carboxyphenyl)-5-methyl2-(naphthathiazolQ- yl)-2Htetrazolium chloride 30 Z-(bcnzothiazol-Z-yl )-3-(p-sulfam ylphenyl )-5-hexyl- 2H-tetrazolium chloride 31 2,3-di( benzothiazol-Z-yl )-S-dodecyl-ZH-tetrazolium chloride 32 2,3-di(pyrid2-yl)-5-hydroxy-2H-tetrazolium chloride 33 2,3-di(benzimidazol-Z-yl)5-mercapto-2H- tetrazolium bromide 34 5-amino-3(benzothiazoLZ-yl)-2 phenyl-2H- tetrazolium chloride 35 5benzamido-3-(4,5-dimethylthiazol-2yl)-2-phenyl-2 H-tetrazolium chloride 36 S-cyano-Z,3-di(benzothiazol-2-yl)-2l-l-tetrazolium chloride 37 S-carboxy-Z,3-ditbenzothiuzol-2-yl)-2H-tetrazolium chloride 38 J-[benzothiazol-Lyl)-5-(4 -hexoxyphenyl)-2'( 3- sulfopheriyl)-2H-tetrazo]ium 39 2-(benzothiazol-Z-yl)-3-phenyl-5[4-(3,5-disulfobenzamido)phenyll-2H-tetrazolium bromide [disodium salt) 40 2-( benzothiazol-Z-yl l-S-t 2-chlorophenyl)-3( 4- nitrophenyl)-2H-tetrazoliurn bromide 41 2-( benzothiazol-Z-yl )-5-phenyl-3-(4-tolyl)-2H- tetrazolium bromide 42 2-(ben2othiazol-2-yl )-3-( 4-chlorophenyl)-5-phenyl-2 Hietrazolium bromide 43 2-(benzothiazol-Z-yl)-5-(4-chlorophenyl)-3-(4- nitrophenyl)-2H-tetrazolium bromide 44 3-(benzothizole-Z-yl)-2phenyl-5(quinol-2-yl)-2H- tctrazolium bromide 45 3-(benzothiazol-Z-yl)-2-phenyl-5-propyl-2H- tetrazolium iodide 46 3-( benzothiazol-Lyl )-2-phenyl-5 {pyrimidine-21*] )-2 H-tetrazolium bromide 47 Z-(naphthimidazol-Z-yl )-3 ,S-diphenyli H tetrazolium acetate 48 3-(benzimidazol-2-yl)-",S-diphenyl-ZH-tetrazolium nitrate 49 3,S-diphenylQ-(pyrid-Lyl)-2H-tetrazolium sulfate 50 2,5-diphenyl-3-(4,5-dirncthylthiazoLZ-yl)-2H- tetrazolium iodide 51 2,3-diphenyl-ZH-tetrazolium thiosulfate 52 2,3-diphenyl-2H-tetrazoliurn thiocyanate These tetrazolium salts are well known in the art, most of them having been described in literature references such as Chemical Revue 55, published bi-monthly for the American Chemical Society by the Williams and Wilkins Co., Baltimore, 1955. Any tetrazolium salts that are not shown specifically in the prior art are advantageously prepared by the methods well known in the art.

When aqueous solutions of our T-salts, brought into contact with metal images of palladium or any metal more easily oxidized (e.g., has an ionization potential more positive than -().98 volt; (e.g., silver, nickel, copper, iron, palladium, zinc, lead, tin, etc. the metal is oxidized to its ion and the T-salt is reduced to produce the corresponding formazan dye. The following equation shows the reaction.

The concentration of our T-salt in our solutions can be varied considerably, with an operable range of concentrations extending from the solubility limit of the T-salt down to a minimum concentration where the overall reaction potential for the specific T-salt and specific metal image just remains positive, usually above +0.01 volt. The operable concentration ranges and the preferred concentration range are readily determined by methods well known in the art and need not be discussed further.

The metal images that are advantageously treated with our T-salt solutions are produced by any of the conventional image-forming methods and especially by photographic methods, using chemical developing out and/or physical developing out materials. The metal image is advantageously made up ofminute particles of metal in a binder, e.g., a hydrophilic colloid such as, gelatin or gelatin substitute, or made of a solid, continuous surface of metal.

The following examples are included for a further understanding ofour invention:

EXAMPLE 1 Several strips of film with a single-layer negative type developing out fine-grain gelatinous silver bromoiodide emulsion coating are flash exposed, black-and-white developed with a conventional aqueous alkaline hydroquinone pmethylaminophenol developer solution to a neutral density of 0.58, fixed in alkali metal hypo solution and washed, are treated for 45 seconds at a temperature of 6570 F. in Solution A having the composition:

T-salt identified in Table l 1.0 g.

Glacial acetic acid 250 ml. Benzyl alcohol 5.0 ml. Water 70.0 ml.

The optical densities of the resulting images to red, green and blue light are tabulated in Table l.

TABLE 1 Images From Fresh TSalt Solution Number of TSalt Used Optical Density oflmage The data in Table 1 show that T-salts according to our invention effectively react with the silver image areas to produce high density formazan dye images. Good formazan dye images are produced when this example is repeated using solutions of our invention described in Table l after being held for 5 days at 120 F. instead of freshly prepared solutions. When this example is repeated using 2-phenyl-3-(4-sulfamylphenyl)-5-(4- hexoxyphenyl)-2H-tetrazolium chloride, 2-tolyl-3,5-diphenyl- 2H-tetrazolium chloride, 2-(2-carboxyphenyl)-5-hexyl-3- phenyl-ZH-tetrazolium chloride, 2,3,S-triphenyl-ZH-tetrazolium chloride, 5,5'-di(4-methoxyphenyl)-2,2-di(4-nitrophenyl)-3,3-di-p-(3,3-dimethoxydiphenylene) di(2H-tetrazolium bromide) and 5,5'-di(2,4-dimethoxyphenyl)-2,2'-diphenyl- 3,3-di-p-(3,3-dimethoxydiphenylene) di(2H-tetrazolium chloride) all outside our invention in place of the T-salts of our invention, no formazan dye image is formed.

Good fomiazan dye images are formed when other T-salts of our invention are used in Example 1 in place of those used therein.

The glacial acetic acid is used in the Solution A of Example 1 as a solvent for the T-salt. The following example shows that our reaction for converting a silver image to a formazan dye image operates at equal rates at pH s of 4, 7.5 and I0.

EXAMPLE 2 Several strips of gelatinous silver halide emulsion coating described in Example 1 are sensitometrically exposed, blackand-white developed to form a good silver image, fixed, washed and dried, and then are each treated with a different portion of Solution B having the composition:

T-salt No. 22 3 g.

Glacial Acetic Acid 300 ml. Benzyl Alcohol ml. Water 62.0 ml.

One portion of Solution B has a pH adjusted to 4.0, another portion is adjusted to a pH of 7.5 and a third portion is adjusted to a pH of 10.0 with 50 percent sodium hydroxide solution in such a way that when large volumes of sodium hydroxide solution are required to adjust the pH, equal volumes of water are added to the other solutions so that all of the active ingredients are present at equal concentrations. Sensitometric curves are plotted relating the formazan dye densities against the exposure for each of the strips treated with the Solution Bs. A comparison of the sensitometric curve shows that the formazan dye images are substantially the same for Solution B at pHs 4.0, 7.5 and 10.0. Similar results are obtained when other T-salts of our invention are used in place of No. 22 in Example 2.

Example 3 demonstrates that it is not necessary to add acid to our T-salt solutions for the conversion of a silver image to a formazan dye image.

EXAMPLE 3 A sample of the gelatin-silver halide film described in Example l is flash-exposed, developed to a silver density of about 0.6 with a conventional aqueous alkaline black-and-white developer solution, fixed with a conventional sodium thiosulfate fix bath, washed, dried and treated in Solution C for 3 min. at 75 C. Optical density values for light of different wavelengths over the range from 400 nm. to 900 nm. are obtained and plotted for the silver image and for the formazan dye image produced by treatment with Solution C. A com-' parison of the curves shows the effective conversion of silver to formazan dye by Solution C which has the composition TSalt No. 22 2.0 g. Dimethylforrnamide 40.0 ml. Water 60.0 ml.

It is well known that spectral changes in formazan dyes can be obtained by complexing the dyes with metal ions. Thus, metal ions added to the processing solutions according to our invention can lead to metal complexes of the formazan dyes directly on reaction with the T-salt with the image silver.

EXAMPLE 4 Several strips of the gelatinous silver halide emulsion coated film of Example 1 are flash exposed, black-and-white developed to a neutral density of 0.58, fixed, washed and treated for 45 seconds at a temperature of 6570 F. in Solution A described in Example 1 and having the T-salt indicated in Table 2. The optical densities recorded through red, green 7 8 and blue filters of the formazan dye images derived from the Potassium dichromate 5.0 g. 0.58 density silver images are given in Table 2, under A. femcyamde Potassium bromide 20.0 g. Under B m Table 2 are tabulated the formazan dye densities in Th e ixing bath has the composition. film strips treated in solutions which differ from those under A Water, so r. (27C.) 1.01. only in that they contain 1.86 g. of copper acetate per 100 ml. 5 Sodium hiosulfm 1500 of solution. Sodium bisulfite 20.0 g.

TABLE 2 The optical densities of the formazan dye or the copper com- A B plex of the formazan dye measured with red, green and blue Images fmm fresh TM 10 light are recorded in Table 3. Images from fresh T-salt sln.+1.8fi g./100 ml. of

solution copper acetate TABLE 3 Optical density of image to Optical densities of image light of indicated 00101 to light of indicated color l Strip R. G. B. Red Green Blue Red Green Blue (L36 H2 L09 0. as 0.68 0. as 0.58 0. 58 0.58 146 0. 60 1. 0e 1. 3s 0. 96 0. 85 0.85 211 (1-81 031 0. s0 0. s0 1. 60 0.82 0.88 0. 02 2b 0.81 0.65 0.81 0. 70 0. 73 0. 73 1. 0 0. s4 0. 77 0. 70 0. 00 0.98 1.18 0 0s 0. 92 0.54 0.60 0. 94 0.72 0.70 0.88 The results show that the formazan dye and copper complex 8' 3g 933 2 33 9-32 8- 3g g g of the formazan dye are substantially unaffected by the color 0. s4 1.' 31 1. 22 1: 10 1 03 1. 05 developer, bleach and fix solutions of the color process. 14 04 90 28 02 The following example illustrates how even low density A silver images are advantageously converted by our process to Good formazan dyes are obtained when this example s revery hi h d i formazan dye i age by u ing the rogre peated using solutions that have been held for 5 days at 120 i l hi h d i ff 1"(PI-ID ffe t).

F. before use. EXAMPLE 6 Good formazan dye or m ta i n C mP X 0 formfllafl A. Several strips of a negative type, developing out, coarsedye images are obtained when other T-salts are used with grain gelatinous silver chlorobromoiode emulsion coated xcopper acetate or the kn n comp ing g 30 ray film containing 115 mg. Ag. and 578 mg. geL/ft are sen- The p characteristics of Certain formazan y sitometrically exposed through a graduated density test obm tal COmPIBXES 0f H1686 y iHdiCate signifimntly g ject, black-and-white developed with a conventional aqueous sorption in the high-wavelength region of the visible and near lk li h d i a d eth lamino henol ulfate infrared p ctrum 50 th th y a useful for m g Sffund developer solution, fixed with a conventional alkali metal tracks monitored by infrared Sensing device$- Thus sllver thiosulfate fixing bath, washed and dried. A strip identified as sound trasks conventional multicolor materials) monistrip 1 is used as a control. Strips identified as 2, 3, 4 and 5 are tored infrared sensing devices are transformed fI'OITl silver treated for 2 4 8 and 16 minutes respectively with T-sah 5011 to formazan dyes or metal complexes of formazan dyes by i fih i h itio treatment in a solution of our invention.

EXAMPLE 5 40 T-salt No. 22 5.0 g.

A first strip of a gelatinous silver halide coated film Glacial acetic acid 250 ml.

described in Example 1 that is flash-exposed and developed to Benz!" 81mm a silver density of 0.6 is treated for 5 minutes at 75 F. in Solu- D having the following composmonz The optical densities of the resulting images to green light are TMRNO. 20 (L06 measured and the D-max. values are reported in Table 4 as Glacial acetic acid 125 m1. follows:

Triethanolamine 0.75 ml.

Benzyl alcohol 0.25 ml.

Water 34.25 mi. 4

A second strip of the film is similar treated, except that Solution D contained, in addition, 0.75 g. of copper acetate. Each Minutes Treab strip is then divided into two parts identified 1a, 1b, and 2a, 2b in Dmax Dans). respectively. Parts 1a and 2a are bleached in a conventional Strip N0 Solution E Green Light alkali metal ferricyanide bleach solution, fixed, washed and dried. Parts lb and 2b are treated in the processing baths 1 0 Comm] 046 (Color development 15 minutes, silver bleaching 8 min., and 2 2 fixing 3 minutes) following the negative development and 2 g reversal exposure in a conventional color process. The color 5 16 developer solution has the composition: 60

The results show that an optimum formazan dye density for a Water 10 F. 21io 27C.) 1- Iv single treatment in the T-salt solution is achieved in 4 minutes. zgf izgg 3% Longer treatment times result in a decrease in dye density. sodium sun-m desiccated B. Three strips of the X-ray film are exposed, developed, Trisodium hosphate 40.0 g. fixed, washed and dned as described in art A of Exam le 6 so P P P a W I V dd 8-3 the silver image has a Dmax to green light of 0.44 density unit. ag gz i f" e 6 One of these strips identified as strip 6 is used as a control. 4-amino-N-ethyl-N-[B-methunesulfonamido-ethyi] m- Strip 7 IS given the treatment outlined below:

loluidinc scsquisulfatc monohydrate 1L3] g. 70 Elhylencdiaminc sulfate 7.8 g. Citrazinic acid l2.6dihydrnxyiso-nicotinic acid) 1.5 Step The bleach solution has the composition: 1 so (on E 4 U l 2 10% acetic acid 3 Water )OF. (32C.) LO l. 3 Water wash 5 4 Developer A 5 acetic acid 6 Wash 7 Solution E 8 10% acetic acid 9 Water wash Bleach A Water wash Fix A Water wash Dry Developer A has the following composition:

Strip 8 is given the same process as strip 7 except that steps 4, 5 and 6 are replaced by a water wash for l 1 minutes. The optical densities of the strips 6, 7 and 8 to green light are measured and the Dmax values are recorded in Table 5 as follows:

Strip Dmax to green light 6 (control) 0.46

The results show that when the silver complex image formed in strip 7 in step I is converted back to silver by step 4 and then subsequently the silver image is again treated with Solution E in step 7 a formazan dye image having a Dmax of2.82 is formed. However in strip 8 the silver complex formed in step 1 is not converted to silver again so the final formazan dye Dmax density is essentially the same as it is in strip 3 in part A of Example 6. Formazan dye densities substantially higher than 2.82 are produced in strip 7 when the strip is taken out of water wash step 9 and sent through steps 4, 5, 6, 7, 8 and 9 again at least once before completion of steps 10 through 14.

Similar results are obtained when example 6 is repeated using other T-salts of our invention in place of T-salt No. 22.

EXAMPLE 7 TABLE 6 Sample No. T-salt No.

In each instance a good formazan dye image is formed in samples 2 through 10. After washing out the residual T-salt from the samples the nickel complex is advantageously reduced back to zero valent nickel by treating with an aqueous solution containing a reducing agent, such as, sodium hypophosphite, sodium borohydride, dimethylamine borane, etc. preferably containing a complexing agent, such as citric acid, maleic acid, etc. and then after thoroughly washing with water the formazan and nickel image is treated again with Solution A to convert the nickel image over to still more formazan dye using the PHD effect described in Example 6.

Similar results are advantageously obtained using other metal images of our invention including copper, cobalt, etc.

This patent application is being filed simultaneously with another patent application in our names which describes and claims a related invention of ours that is concerned with replacing a metal image with a formazan dye image by contacting the metal image with a solution of a metal complexing agent in the presence of a T-salt and concerned with blix compositions containing a combination of a T-salt and a metal complexing agent.

The invention has been described in detail with particular reference to preferred embodiments thereof, but, it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. A process'for converting at least a part of a zero valent metal image to a formazan dye image by the step of contacting said metal image with an aqueous solution containing a watersoluble, diffusible tetrazolium salt which has at least one moiety that is a metal ion complexing agent, such that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least+0.0l volt.

2. A process for converting at least a part of a zero valent metal image to a formazan dye image by the step of contacting said metal image with an aqueous solution containing a watersoluble, diffusible tetrazolium salt which has at least one moiety that is a metal ion complexing agent, such that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least +0.01 volt, said tetrazolium salt being represented by the formulas:

wherein R and R each represent a group selected from the class consisting of an aryl group and a heterocyclic group; R represents a member selected from the class consisting of hydrogen, an alkyl group, an aryl group, a heterocyclic group, hydroxyl, carboxyl group, a salt of carboxyl group, a carboxyester group, an amino group, a carbamyl group, sulfo, a salt of the sulfo group, a sulfonamido group, a sulfamyl group, the mercapto group and the nitro group; X represents an anion, such that at least one of R R and R and X 0 contains a metal ion complexing agent; D represents a divalent aromatic group; 5 and E represents a divalent group selected from the class consisting of an alkylene group, an arylene group and an antikylene group; n represents an integer of from l to 5; said metal image being oxidized to metal ions by said tetrazolium salt which is reduced to the corresponding formazan dye, said formazan dye being nondifiusible.

3. A process of claim 1 in which said metal image is a silver image.

4. A process of claim 2 in which said metal image is a silver image.

5. A process for converting at least a part of a zero valent metal image to a formazan dye image by the step of contacting said metal image with an aqueous solution containing a watersoluble, diffusible tetrazolium salt which has at least one moiety that is a metal ion eomplexing agent, that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least +0.0l volt, said tetrazolium salt being represented by the formulas:

wherein R and R each represent a group selected from the class consisting of an aryl group and a heterocyclic group; R

represents a member selected from the class consisting of hydrogen, an alkyl group, an aryl group, a heterocyclic group, hydroxyl, carboxyl group, a salt of carboxyl group, a carboxyester group, an amino group, a carbamyl group, sulfo, a salt of the sulfo group, a sulfonamido group, a sulfamyl group, the mercapto group and the nitro group; such that at least one of R,, R and R represents a metal-ion-complexing heterocyclic group selected from the class consisting of a 4,5-dialkylthiazol-Z-yl group, a benzothiazol-Z-yl group, a naphthothiazol-Z-yl group and a benzimidazol-Z-yl group; X represents an anion; D represents a divalent aromatic group; and E represents a divalent group selected from the class consisting of an alkylene group, an arylene group and an aralkylene group; n represents an integer of from 1 to 5; said metal image being oxidized to metal ions by said tetrazolium salt 60 which is reduced to the corresponding nondiffusible formazan dye and said metal ion is complexed by said metal-ion-complexing heterocyclic group.

6. A process of claim 5 in which the tetrazolium salt has the formula:

N N m n-1 7. A process for converting a silver image in a hydrophilic colloid layer to a formazan dye image comprising the step of contacting said metal image with an aqueous solution of 2- (benzothiazol yl) 5 (2 chlorophenyl) 3 phenyl 2H tetrazolium bromide.

8. A process for converting a silver image in a hydrophilic colloid layer to a formazan dye image comprising the step of contacting said metal image with an aqueous solution of 2- (benzothia2ol-2-yl )-5-phenyl-3-( 4-tolyl )-2H-tetrazolium bromide.

9. A process for converting a silver image in a hydrophilic colloid layer to a formazan dye image comprising the step of contacting said metal image with an aqueous solution of 2- (benzothiazol 2 yl) 5 (4 acetamidophenyl) 3 (4 phenyl azolphe n l)2H-tetra zolium bromide.

10, A process or converting a silver image in a hydrophilic colloid layer to a fonnazan dye image comprising the step of contacting said metal image with an aqueous solution of 2- (4,5-dimethylthiazol-2-yl)-3,5-diphenyl-2l-l-tetrazolium bromide.

11. A process for converting a metal image to a formazan dye image having a substantially higher image density, com prising the steps of: I

l. contacting said metal image with an aqueous solution containing a water-soluble diffusible tetrazolium salt which has at least one moiety that is a metal ion complexing agent such that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least +001 volt, so said metal image is oxidized to the corresponding metal ion complex and said tetrazolium salt that oxidized said metal image is reduced to a corresponding formazan dye image,

2. washing in water to remove residual tetrazolium salt solution,

3. reforming said metal image by converting said complexed metal ion image to a corresponding metal image, and

4. contacting said reformed metal image with an aqueous solution containing a water-soluble, difiusible tetrazolium salt which has at least one moiety that is a metal ion complexing agent such that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least +0.01 volt, so said reformed metal image is oxidized to the corresponding metal ion complex and said tetrazolium salt that oxidized said reformed metal image is reduced to a corresponding formazan dye image thus increasing the formazan dye image density formed in step 1. 

2. A process for converting at least a part of a zero valent metal image to a formazan dye image by the step of contacting said metal image with an aqueous solution containing a water-soluble, diffusible tetrazolium salt which has at least one moiety that is a metal ion complexing agent, such that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least +0.01 volt, said tetrazolium salt being represented by the formulas:
 2. washing in water to remove residual tetrazolium salt solution,
 3. reforming said metal image by converting said complexed metal ion image to a corresponding metal image, and
 3. A process of claim 1 in which said metal image is a silver image.
 4. A process of claim 2 in which said metal image is a silver image.
 4. contacting said reformed metal image with an aqueous solution containing a water-soluble, diffusible tetrazolium salt which has at least one moiety that is a metal ion complexing agent such that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least +0.01 volt, so said reformed metal image is oxidized to the corresponding metal ion complex and said tetrazolium salt that oxidized said reformed metal image is reduced to a corresponding formazan dye image thus increasing the formazan dye image density formed in step
 1. 5. A process for converting at least a part of a zero valent metal image to a formazan dye image by the step of contacting said metal image with an aqueous solution containing a water-soluble, diffusible tetrazolium salt which has at least one moiety that is a metal ion complexing agent, that the combination of said metal and said tetrazolium salt in the presence of water produces a solution reaction potential of at least +0.01 volt, said tetrazolium salt being represented by the formulas:
 6. A process of claim 5 in which the tetrazolium salt has the formula:
 7. A process for converting a silver image in a hydrophilic colloid layer to a formazan dye image comprising the step of contacting said metal image with an aqueous solution of 2-(benzothiazol-2-yl)-5-(2-chlorophenyl)-3-phenyl-2H-tetrazolium bromide.
 8. A process for converting a silver image in a hydrophilic colloid layer to a formazan dye image comprising the step of contacting said metal image with an aqueous solution of 2-(benzothiazol-2-yl)-5-phenyl-3-(4-tolyl)-2H-tetrazolium bromide.
 9. A process for converting a silver image in a hydrophilic colloid layer to a formazan dye image comprising the step of contacting said metal image with an aqueous solution of 2-(benzOthiazol-2-yl)-5-(4-acetamidophenyl)-3-(4-phenylazolphenyl)-2H -tetrazolium bromide.
 10. A process for converting a silver image in a hydrophilic colloid layer to a formazan dye image comprising the step of contacting said metal image with an aqueous solution of 2-(4,5-dimethylthiazol-2-yl)-3,5-diphenyl-2H-tetrazolium bromide.
 11. A process for converting a metal image to a formazan dye image having a substantially higher image density, comprising the steps of: 